Light diffusors



June 11, 1963 E, F. GUTH, JR 3,093,323

LIGHT DIFFUSORS Filed Oct. 12, 1961 5 Sheets-Sheet 1 [ml w 5 WM 412,

June 11, 1963 F. GuTH, JR 3,093,323

LIGHT DIFFUSORS Filed Oct. 12, 1961 3 Sheets-Sheet 2 United States Patent 3,093,323 LIGHT DHFUSORS Edwin F. Guth, .ln, Ladue, M0., assignor to The Edwin F. Guth (Iompauy, St. Louis, Mo., a corporation of MISSOul'i Filed Oct. 12, 1961, Ser. No. 144,674 4 Claims. (Cl. 24tl78) This invention relates to light diifusors for illuminating devices and more particularly to light difiusors, such as shown in the patent to Edwin -F. Guth, Sr., No. 2,904,673 of September 15, 1959. This patent shows a ditfusor for a lighting fixture which may take several forms, all of which can be characterized as louvers or lattices with spaced longitudinal elements and spaced transverse eleanents of prismatic form. Louvers of this kind, constructed in accordance with the description in this patent, made excellent diifusors for light from fluorescent tubes especially and have been more than acceptable in the field of lighting. This is so because it is possible to obtain a soft lighting effect of a high intensity from lamps of lower rating. One characteristic of this diifusor is that when the diffuser is viewed from the end of the fixture lengthwise, the image of the lamps appears to the viewer. The difiusor, in other words, creates the impression that the lamps are exposed below the grid when viewed in this manner and from the end of the fixture. This has been a disadvantage and one which prevented extending the use of this type of diifusor over an entire ceiling.

One of the objects of this invention, therefore, is an improvement in the patented diffusor which will eliminate the transmission of an image of the lamps.

Another object of this invention is an improvement in the patented difiusor to ornament its appearance without interfering with the efiiciency of light transmission.

According to this invention, the diffusor comprises a lattice-like structure of light transmitting material which is preferably transparent. The lattice is formedj by spaced longitudinal elements and spaced transverse elements of prismatic shape intersecting one another at right angles to form therebetween a multiplicity of apertures for a grid-like structure. The longitudinal elements in the grid-like structure are so described because they run parallel with the lighting tube, or tubes, in the lighting fixture, although the grid may be wider in the direction of the transverse elements than in the direction of the longitudinal elements. v

As stated in the aforesaid patent, the walls of both longitudinal and transverse elements are formed to deflect the light incident on the lattice in a variable manner by both refraction and reflection from one side to the other thereof. The amount and kind of deflection depends upon the prism shape of the longitudinal and transverse elements. The open spaces between these elements may be described as that of a truncated geometric solid of the character represented by a pyramid, a hemisphere or a cone whose directrix may be either polygonal or curvilinear, and whose generatrix may be either a series of straight lines, or a curved line. In this type of a grid structure, diffusion will take place because of the multiplicity of prism shaped elements. The only objectionable feature, as aforementioned, is that, when viewed longitudinally from beneath the diifusor, an image of the lighting tube appears adjacent its opposite, or under, surface. In the improved device disclosed in this application, the image is eliminated. This result is accomplished by properly spaced undulations or V-shaped grooves parallel to the length of the longitudinal elements and to the lighting tube within the lighting fixture. Preferably these undulations or V-shaped grooves cover the entire lower surface of the grid. Additional grooves can extend 3,993,323 Patented June 11, 1963 "ice transversely, if desired, so that the grid may be placed in any relation with respect to the lighting tube within the fixture.

Other objects and advantages will appear to those skilled in the art from the following detailed description which is in such clear, concise and exact terms as will enable any one to construct and use the same when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an illuminating device provided with a light controller or diffusor constructed in accordance with this invention;

FIG. 2 is a perspective view of one embodiment of the ligit controller or diffusor structure, such as shown in F1 1;

FIG. 3 is a fragmentary view in cross-section showing a light diffuser and tube on an enlarged scale illustrating why a diffusor with plane surfaced prismatic elements transmits an image of the lighting tube to one positioned below the diifusor and looking endwise thereof;

FIG. 4 is an end view of the structure shown in FIG. 3 illustrating the appearance of this structure when viewed from one end;

FIG. 5 is a fragmentary perspective view of the improved form of light diifusor illustrated on an enlarged scale to show the lighting efiect produced by this invention as contrasted with the prior invention in FIG. 4; and

FIG. 6 is a similar view to FIG. 5 of a second, or modified form of the invention.

Referring to the accompanying drawings, and more particularly to FIG. 1, a lighting fixture 1 may be supported in a suitable manner in a ceiling 2 of a room. Within the lighting fixture are shown sockets 4, 4 which support the lighting tubes 5, 5. A suitable frame 6 attached to the fixture 1 is adapted to support the diffusor It beneath the lamps 5 which are fluorescent type tubes. The lamps are, therefore, in a position to direct rays of light directly to the top face ill of the diffusor, or grid, and through the apertures therein.

As illustrated in the figures in the drawing, each dilfusor consists of a series of preferably transparent prisms 12 spaced apart and extending lengthwise of the diifusor, and a series of prisms 14 also spaced apart and extend transversely to the longitudinal elements 12 so as to define between a series of frusto-pyramidal open spaces 15. The lattice-like structure or grid 10 may be manufactured of any size, or it may be manufactured in a standard size, and one or more of these standard sizes be placed edge to edge in order to cover the opening in a light fixture 1.

The practical embodiment of the lattice-like structure may be three-eighths inch thick from top face to bottom face. The prism shape of the longitudinal and transverse elements may be such as to leave apertures one-quarter inch on a side at the bottom face and a half inch on a side at the top face. In order to obtain best results, the included angle at the apex of each prism should be between 34 and 45, preferably about 37. Such an arrangement will provide a structure in which the apices of each of the prisms are spaced about a half inch apart, and, of course, the bottom of the prisms will be spaced about half that distance. These dimensions may, however, be varied to suit various conditions. The bottom surface of the lattice-like structure 10 is grooved longitudinally, as shown in FIGS. 2 and 5, to define a plurality of regular V-shaped ribs and grooves extending longitudinally across the lower face. These grooves have side faces inclined at an angle of to one another and are approximately five hundredths of an inch in depth. Grooves of this dimension will form a surface on the lower side of each of the longitudinal elements which has two and a half grooves, indicated as 24, 25 and 26, the surface will also have a like number of ribs between the grooves and indicated as 27, 28 and 29. The bottom of groove 25 is preferably offset slightly from the center line of the longitudinal element an amount approximately .018 inch. Thus, the grooves and ribs are regular in shape but in unsymmetrical relation to the prism shaped elements of the grid. This pattern is repeated regularly on each of the longitudinal elements. Between longitudinal elements, the transverse elements have a similar arrangement and spacing of grooves and ribs so that there are two and a half ribs, that is, half of rib 29, rib 32 and rib 34 in the transverse element making two and a half ribs. Likewise, there are two and a half grooves 33, 35 and half of groove 37. This pattern is repeated on each transverse element. Each of the ribs between the grooves are prisms capable of reflection and refraction to disperse the light rays in a manner transversely of the grid or panel for a purpose which will be hereinafter described. Their effect upon total light transmission is negligible and the result in appearance is distinctly novel. The reason for this will appear from a consideration of the schematic illustration in FIGS. 3 and 4 of the drawings.

Turning now to these figures, 3 and 4, FIG. 3 illustrates diagrammatically a relationship between a lighting tube 5 and a lighting panel, such as shown in the aforesaid patent, which has longitudinal and transversely spaced prism members, indicated as A and B, respectively. These prism members are preferably transparent and in the arrangement described define frusto-pyramidal openings C, all in the manner as heretofore described. Lighting tube 5 transmits a plurality of rays R downwardly against the prism surface S of the transversely extending elements of prismatic form A in a manner as illustrated in FIG. 3. These rays, or some of them which are not reflected, penetrate the surface S and are refracted angularly against the surface S2. Those of the rays, which are reflected from the surface S2, emerge from the surface S3 in approximately the identical pattern in which they entered the prism A in the first place to create the phantom image 5' of the lighting tube 5. Since these rays are visible only from a position lengthwise of the lighting tube 5, that is, when the panel is viewed from one of its ends, then the image 5 is visible only from such a position. Nevertheless, the image is so distinct when the fixture is viewed lengthwise that many people are deterred from installing this type of ceiling panel. In a small lighting fixture, the effect is not so noticeable.

As stated beforehand, there is also not only an improvement in that the image 5' is eliminated, but also an improvement in the appearance and uniform lighting transmitted from the lighting panel of the light transmitting device. This improvement in appearance is illustrated by the comparison between FIGS. 4 and 5, which are, respectively, the lighting panel, or light transmitting device, shown in FIG. 3 and the lighting panel, or light transmitting device, shown in FIG. 2. Referring to FIG. 4, from a position viewing the panel endwise of the lighting tube, the surfaces S2 of each of the transverse prism elements A appear bright. This gives the effect that the panel, shown in FIG. 3, is composed of a plurality of inverted frusto-pyramidal members arranged in parallel rows. The lighting panel shown in FIG. 5 presents an entirely different appearance as this illustration shows. The addition to the lower surface of the light transmitting device of rows of unsymmetrically arranged prisms extending lengthwise of the panel and parallel to the lighting tube changes the appearance the lighted panel in a marked degree. This will be readily recognized by mere comparison.

In order to attain the satisfactory appearance and advantages described relative to the panel shown in FIG. 5, it must be installed with the small prisms on its lower face extending parallel with the lighting tube 5. Since this may be a disadvantage in some installations, a panel was developed in which the small prisms on the lower face extend both longitudinally and transversely. FIG. 6 shows a fragmentary view of the lower surface of the same panel so modified. Turning to FIG. 6, which shows this modified form, the longitudinal ribs and grooves, extending parallel to the lighting fixture which are the same as in the modification shown in FIG. 5, are indicated by like reference characters. The transversely extending ribs and grooves parallel to and on the lower surface of each of the transverse extending prism shaped elements are indicated by the reference characters 44, 45, 46 for the grooves and 47, 48 and 49 for the ribs. Both modifications, that shown in FIG. 5 and that shown in FIG. 6, have prisms of regular shape unsymmetrically arranged with respect to the longitudinal and transverse elements of the grid, or lighting panel, otherwise the lightcontrolling panel is constructed in the same manner as in the aforesaid patent. From the foregoing description, it will be understood that this invention accomplishes its objects by eliminating one of the objectionable characteristics of the prior patented panel as well as improving its general appearance when lighted.

Changes in and modifications of the construction described may be made without departing from the spirit of my invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In a light-controlling panel having a lattice of elongate intersecting prisms of substantially transparent material formed of spaced longitudinal elements and spaced transverse elements defining a multiplicity of generally frusto-pyramidal openings through the panel, said prisms being substantially triangular in cross-section and having their apices at the upper surface of the panel disposed in the plane of the larger base of said frustopyramidal openings, wherein the angle included between the convergent surfaces of said prisms which define said apices being between thirty-four and forty-five degrees and the base of said prisms form the lower surface of the panel, the improvement comprising a plurality of regular grooves and ribs disposed parallel to the longitudinal elements and forming a continuous corrugated lower surface on said prisms.

2. In a light-controlling panel having a lattice of elongate intersecting prisms of substantially transparent material formed of spaced longitudinal elements and spaced transverse elements to define a multiplicity of generally frusto-pyramidal openings extending entirely through the panel, said prisms being substantially triangular in cross section and having their apices located at the top surface thereof substantially in the plane of the larger base of said frusto-pyramidal openings, wherein the altitude of the frusto-pyramidal openings corresponds approximately to apex spacing between adjacent parallel elongated prisms and the prisms have an angle included between the convergent surfaces thereof which define said apices being between thirty-four and forty-five degrees, the improvement comprising a plurality of regular grooves and ribs therebetween formed across the base surfaces of said prisms and extending parallel to the longitudinal elements.

3. In a light-controlling panel having a lattice of elongate intersecting prisms of substantially transparent material formed of spaced longitudinal elements and spaced transverse elements, said prisms being spaced to define a multiplicity of generally frusto-pyramidal openings extending entirely through the panel from the top face to the bottom thereof, with the openings at the lower surface substantially square and having a side dimension corresponding approximately to the base dimension of the prisms, said prisms being substantially triangular in cross-section with their apices at the upper sur face of the panel in the plane of the larger base of said frusto-pyrarnidal openings, and the angle included between convergent surfaces of said prisms which define said apices being between thirty'four and forty-five degrees,

the improvement comprising a plurality of grooves disposed in the bases of said prisms forming regular ribs extending parallel with said longitudinal elements.

4. In a light-controlling panel having a lattice formed of interconnected prisms including spaced longitudinal prism elements and spaced transverse prism elements intersecting one with the other to form interconnected prisms defining a multiplicity of openings extending e11- tirely through the panel from the top surface thereof to the bottom surface, with the openings being formed of uniform shape and size, said prisms being formed of clear material having light-refracting and light-reflecting properties and being of triangular cross-section with their vertices at the top surface of said panel and their bases at the bottom surface thereof and the vertex angle of said prisms being approximately thirty-seven degrees, the improvement comprising a plurality of spaced ribs of regular shape formed by grooves extending along the under surface of said panel parallel with said longitudinal elements nad unsymmetrically arranged with respect to the base of the prisms of the longitudinally extending elements.

References Cited in the file of this patent UNITED STATES PATENTS 458,850 Jacobs Sept. 1, 1891 2,318,716 Rolph May 11, 1943 2,398,507 Rolph Apr. 16, 1946 2,558,422 De Leo June 26, 1951 2,904,673 Guth Sept. 15, 1959 2,927,994 Guth Mar. 8, 1960 2,977,460 Franck Mar. 28, 1961 FOREIGN PATENTS 1,101,318 Germany Mar. 9, 1961 

1. IN A LIGHT-CONTROLLING PANEL HAVING A LATTICE OF ELONGATE INTERSECTING PRISMS OF SUBSTANTIALLY TRANSPARENT MATERIAL FORMED OF SPACED LONGITUDINAL ELEMENTS AND SPACED TRANSVERSE ELEMENTS DEFINING A MULTIPLICITY OF GENERALLY FRUSTO-PYRAMIDAL OPENINGS THROUGH THE PANEL, SAID PRISMS BEING SUBSTANTIALLY TRIANGULAR IN CROSS-SECTION AND HAVING THEIR APICES AT THE UPPER SURFACE OF THE PANEL DISPOSED IN THE PLANE OF THE LARGER BASE OF SAID FRUSTOPYRAMIDAL OPENINGS, WHEREIN THE ANGLE INCLUDED BETWEEN THE CONVERGENT SURFACES OF SAID PRISMS WHICH DEFINE SAID APICES BEING BETWEEN THIRTY-FOUR AND FORTY-FIVE DEGREES AND THE BASE OF SAID PRISMS FORM THE LOWER SURFACE OF THE PANEL, THE IMPROVEMENT COMPRISING A PLURALITY OF REGULAR GROOVES AND RIBS DISPOSED PARALLEL TO THE LONGITUDINAL ELEMENTS AND FORMING A CONTINUOUS CORRUGATED LOWER SURFACE ON SAID PRISMS. 